Burner-blower combination for grain dryers



Oct. 9, 1962 T. J. BJERKAN BURNER-BLOWER COMBINATION FOR GRAIN DRYERSFiled Feb. 15, 1960 3 Sheets-Sheet l INVEN TOR. 7776000/6 J dyer/faAffamey Get. 9, 1962 T J. BJERKAN 3,057,611

BURNER-BLOWER COMBINATION FOR GRAIN DRYERS Filed Feb. 15, 1960 3Sheets-Sheet 2 JNVENTOR. 771600'0/2 J fijrr/Esw Affarnay Oct. 9, 1962 r'r. J. BJERKAN 3,057,611

BURNER-BLOWER COMBINATION FOR GRAIN DRYERS I Filed Feb. 15, 1960 Y 3Sheets-Sheet 3 I INVENTOR. 726002,? J @Pr/fan QMdM A ffarncy.

United States Patent U 3,057,611 BURNER-BLOWER COMBINATION FOR GRAINDRYERS Theodore J. Bjerkan, Prairie Village, Kans., assignor to BjerkanEngineering Service, Inc., Prairie Village, Kans., a corporation ofMissouri Filed Feb. 15, 1960, Ser. No. 8,542 8 Claims. (Cl. 263-19) Thisinvention relates to new and useful improvements in burner-blowercombinations for use in connection with grain dryers and the like, andhas as its principal object the provision of means for automaticallyproportioning the primary and secondary air supplied to the burner formaximum efiiciency of fuel combustion despite variations in the staticpressure head against which the blower may be operating.

In a common form of grain dryer, heated air is forced through a bed ofgrain disposed in a grain bin or the like, the air being propelled by ablower disposed in a conduit interconnected with the bin, and heated bya burner also disposed in said conduit and supplied with gas or otherfuel. The blower also supplies the air for combustion, and the largeamount of air delivered by the blower when operating against a lowpressure head is such that little or no primary mixture of air and fuelbefore the fuel leaves the burner is required. However, when the grainbed is thicker or the grain is wetter and denser, greater pressure isrequired to force the air therethrough, and the blower must operateagainst a greater static head. As a result, less air is drawn throughthe conduit, and poor combustion of the fuel will result, causing anexpensive waste of fuel, and carboning of the burner parts. Under suchconditions the efliciency of combustion may be maintained if a greaterproportion of primary air is delivered to the burner. The presentinvention contemplates means for delivering primary air to the burnerautomatically in proportion to the static head against which the bloweris operating. That is, the greater said static pressure, the moreprimary air will be delivered to the burner.

Another object is the provision, in a burner-blower combination of thecharacter described, of -a burner and baffle arrangement for producinggood flame retention characteristics despite the high velocity of airadjacent thereto, that is, for causing the flame to burn directlyadjacent the burner face. Separation of the flame from the burner facecauses excessively noisy operation, may cause the flame to be blown orsnuffed out, and may cause pulsation of the flame with vibration whichmay be injurious to the structure.

A further object is the provision of a device of the character describedwherein the blower and the burner are disposed in independent andseparable casings, and the further provision of means whereby a singleburner casing may be mounted selectively on blower casings of severaldifferent diameters without loss of burner efficiency. Thus a pluralityof bins of diflerent sizes, wherein the blower diameter is determined bythe bin size, may be serviced by a single burner.

Other objects are simplicity and economy of construction, efficiency anddependability of operation, and adaptability for use in applicationsother than grain drying.

With these objects in view, as well as other objects which will appearin the course of the specification, reference will be had to thedrawing, wherein:

FIG. 1 is a side elevational view, partially broken away, of a grain binhaving a burner-blower combination embodying the present inventiondisposed in operative relationship thereto,

Patented Oct. 9, 1962 FIG. 2 is an enlarged fragmentary sectional viewtaken on line II-II of FIG. 1 with parts left in elevation,

FIGS. 3 and 4 are slightly reduced sectional views taken respectively onlines III-III and IVIV of FIG. 2,

FIG. 5 is a sectional view taken on line VV of FIG. 2, and

FIG. 6 is an enlarged sectional View taken on line VI-VI of FIG. 2.

Like reference numerals apply to similar parts throughout the severalviews, and the numeral 2 applies to a grain bin having a cylindricalvertical wall 4, a roof 6 spaced above wall 4 by brackets 8 to provide aventilating opening 10 therearouud, a floor 12, and a perforated falsebottom 14 spaced above floor 12 to form a plenum chamber 16therebetween. Grain 18 to be dried is supported on the false bottom.Communicating with chamber 16 is a conduit 20, to the open outer end ofwhich is attached, successively, a blower housing 22 and a burnerhousing 24, said burner and blower housings in conjunction constitutingsingle tubular housing. Details of the blower and burner constructionare shown in FIGS. 2-6.

Blower housing 22 is cylindrical in form, being open at both ends, andis interconnected at one end to conduit 20 by a bolted flange connection26, or any other suitable connecting means. At its opposite end, housing22 is also provided with a flange 28, and the end of the housing iscovered by a wire screen 30, said screen being secured against the faceof flange 28 by means of an annular face plate 32 and rivets 34.Disposed concentrically in housing 22 is an electric motor 36, saidmotor being mounted on a shelf 38 extending across and welded at itsends to said housing. The shaft 40 of said motor is coaxial with thehousing, and has a fan or blower 42 keyed thereto. Said fan is operablewhen actuated to deliver air through conduit 20 into plenum chamber 16,thence upwardly through the perforations of false bottom 14 and throughthe bed of grain 18, and finally out of the bin through opening 10.Housing 22 is also fitted with a small pipe 44 fixed in the wall thereofso as to communicate with the interior of the housing just ahead of,that is at the delivery side of, fan 42. Said pipe supplies primary airto the gas burner, as will be described below.

Burner housing 24 is also cylindrical in form and open at both ends,being disposed in coaxial relation with blower housing 22 and inend-to-end relationship therewith. It is attached to the blower housingby means including a plurality of radially extending fins 46 affixed tothe external surface thereof at angularly spaced intervals. A hook 48engaging flange 28 of housing 22 is secured to each of said fins by abolt 50 which is inserted selectively in any one of a series of radiallyspaced apart holes 52 formed in said fin. It will be apparent that bymounting bolts 50 in different holes 52, the burner housing may bemounted on blower housings of different diameters.

Supported in housing 24, co-axially therewith is a burner ring 54. Saidburner ring is annular in form, having an external diameter smaller thanthat of housing 24, whereby 'to leave an annular lair passage 56there-between (see P16. 5 Said burner ring is provided at angularlyspaced intervals with integral lugs 58 (see FIG. 5) which extendradially outwardly and are securedto housing 24 by screws 60. Saidburner ring has a circular gas passage 62 which is adapted to direct theprimary air-gas mixture forwardly from the face 64 of the burner througha ring of holes 66 and through an annular opening 68, the major portionof the mixture passing through opening 68. The ring is provided with anintegral cylindrical extension 70 which forms the inner wall of annularopening 68 and which projects somewhat forwardly of face 64 of the ring.Disposed in the forward portion of housing 24, coaxially form an airpassage 73 therebetween (see FIG. 2).

therewith, is a cylindrical tube 72, of smaller diameter than theinternal diameter of the burner ring. The forward end of said tubeextends nearly flush with the forward end of housing 24, and issupported concentrically therein by tie rods '74 connected to thehousing. The rearward end of said tube extends within the burner ringand is fitted with a forwardly divergent conical baffle 76. The rearwardedge of said baflle is joined to tube 72 around the entire peripherythereof, and the forward portion of the bafiie extends forwardly ofextension 70 of the burner ring in spaced relation therefrom, whereby toSaid baffle is connected to and supported by the burner ring, by meansof a plurality of Welded brackets 30 which do not appreciably affect theflow of air through passage 78.

The primary air-gas mixture is supplied to passage 62 of the burner ringthrough a pipe 82 interconnected therewith through the rearward face ofthe burner ring. Said pipe is interconnected at its outer end with oneof the end outlets of a T-fitting 84. A gas supply pipe 86 isinterconnected in the side inlet of said T-fitting, and is fitted withthe usual gas orifice member 88. The other end inlet of said T-fittinghas connected therein a short pipe 90 in which is installed aflow-regulating butterfly valve )2. As shown in FIG. 6, said valveconstitutes a flat circular plate mounted on a stem 94 which extendsthrough a bushing 96 aflixed to the pipe and which may be turnedmanually by a handle 98 aflixed thereto. A flexible hose 100 isconnected at one end to the outer end of pipe 90 by a hose clamp 102,and is connected at its opposite end to theouter end of pipe 44 by hoseclamp 104. The hose is preferably disposed externally to the blower andburner housings, as shown. It will be understood also that the burnermay be provided with the usual control and safety devices, such as amain valve, a pilot burner, and means for shutting the main valve if thepilot burner or the blower should fail. However, such devices form noessential part of the present invention, and are therefore not shown.

In use, it will be apparent that when motor 36 is started and the burneris lighted, the fan 4-2 will draw air into the rearward end of burnerhousing 24, and that the air will then flow through passages 56 and 78to supply secondary air for complete combustion of the primary mixtureemerging from the burner ring. The hot gaseous products of combustion,and air heated thereby, will then be forced by the fan through conduitand through the bed of grain 18 as previously described, whereby saidgrain is dried. The fan will necessarily operate against a staticpressure in conduit 29, the degree of this pressure depending primarilyon the depth and density of the grain bed. This static pressure forcesair through hose 100 to supply primary air to T-fitting 84, wherein itis intermixed with the gas before it enters the burner ring. When thestatic pressure is low, as is the case when the grain bin is onlypartially filled, very little primary air is required, since the volumeof air being drawn through the housings is relatively large and will besufficient for eflicient combustion. It will be seen that at this timethe low static pressure will deliver only a small amount of air throughhose 1%. Correspondingly a high static pressure head on the fan, as whenthe bin is more nearly full, will decrease the amount of air drawnthrough the housing by the fan, to the point where ineflicientcombustion and carboning of the burner parts could occur. This higherstatic pressure causes more air to be delivered through hose 100,whereby the air-gas ratio for efficient combustion is maintained. Inother words, the primary air delivered varies directly with the staticpressure against which the blower is operating, and the proper air-gasratio is maintained automatically.

Butterfly valve 92 serves to initially regulate the primary air flow foroptimum operation. However, once this setting has been determined for agiven installation, it need not be further adjusted, since in allsubsequent operation the primary air flow will be regulated byvariations in the static air pressure ahead of the blower fan, asdescribed.

The relationship of conical baffle member 76 to the burner ring has beenfound to produce a burner having good flame retention characteristics,in that the flame commences at or very close to the burner face 64. Ashas been pointed out, separation of the flame from the burner facecauses ineflicient combustion, noisy operation, and possibly damagingpulsation or vibration. The provision of a special flame retention meansis of peculiar and special importance in a grain dryer device as shown,or other similar applications, in that for efficient drying a greatexcess of air over that actually required for combustion is necessary.The resultant high velocity of the air flowing past the burner wouldtend to cause flame separation it special provision were not made toprevent it. In the present structure, baffle 76 directs a conical wallof air forwardly so as to intersect angularly the substantiallycylindrical wall of the air-gas mixture emerging from burner opening 68,and also the substantially cylindrical wall of secondary air flowingpast the burner through annular passage 56. This angular relation causesan extreme flow turbulence, which produces rapid and thoroughinermixture of the secondary air and primary air-gas mixture, with theresult that the flame burns evenly from the face of the burner ring. Theextension 70 of the burner ring prevents the conical Wall of airdelivered by battle 76 from inhibiting the actual exit of the primaryairgas mixture from the burner. Also, it will be seen that air drawnforwardly through tube 72 is substantially unheated, and since the tubeis in alignment with electric motor 36, it envelopes said motor at alltimes with relatively cold air, whereby to protect said motor fromdamage by overheating by the burner flame.

Another advantage of my structure is that it permits a single burnerassembly to be mounted interchangeably on blower housings of varioussizes, so long as the blower housing is at least as large as the burnerhousing, without loss of blower capacity or burner efliciency. When theburner housing is smaller than the blower housing, the blower intakeincludes the annular portion of the rearward end of its housing whichsurrounds the burner housing. Therefore the blower intake is notrestricted nor its capacity reduced by the small burner housing. At thesame time, the burner housing passes substantially the same quantity ofair as it would if it were the same size as theblower housing, so thatthe large blower does not increase the air velocity in the burnerhousing, which otherwise would interfere with the burner efliciency. Inother words, changes in the diameter of the composite conduit formed bythe two housings, caused by the fact that the burner housing may besmaller than the blower housing, will not effect the efficiency of thedevice so long as the burner housing does not appreciably obstruct orrestrict the intake end of the blower housing.

While I have shown and described a specific embodiment of my invention,it will be readily apparent that many minor changes of structure andoperation could be made without departing from the spirit of theinvention as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. In combination, a substantially tubular housing having an air inletend and an air outlet end, a blower mounted in said housing intermediateits ends and operable to impel a current of air through said housingfrom its inlet end to its outlet end, a fluid fuel burner mounted insaid housing intermediate said blower and the inlet end of said housingand operable to eject fuel into said housing whereby when said fuel isignited said air will be heated, said air supplying secondary combustionair for said burner, and means for mixing primary combustion air withsaid fuel prior to its ejection from said burner, said means comprisinga conduit interconnected at its one end to said burner, andinterconnected at its opposite end into said housing intermediate saidblower and the outlet end of said housing, said conduit opening intosaid housing at right angles to the axis thereof, so that air flowingthrough said conduit to said burner varies generally in directproportion to the static air pressure in said housing.

2. The combination as recited in claim 1 with the addition of anadjustable flow regulating valve in said conduit.

3. The combination as recited in claim 1 with the addition of bafllemeans mounted in said housing and operable to direct a portion of theair flowing through said housing in angularly intersecting relationshipto the primary air-fuel mixture emerging from said burner, closelyadjacent its point of emergence therefrom.

4. The combustion as recited in claim 1 wherein said burner is ringshaped and directs the primary air-fuel mixture forwardly therefrom, ina substantially cylindrical configuration, and with the addition of aconical baflle plate mounted in the open center of said burner ringconcentrically therewith and diverging forwardly, said baflle plateterminating at its forward edge forwardly of said burner, whereby todirect a conical wall of air in angularly intersecting relation to theprimary air-fuel mixture emerging from said burner.

5. The combination as recited in claim 1 wherein said burner is disposedintermediate said blower and the inlet end of said housing and is drivenby an electric motor mounted centrally in said housing, and wherein saidburner is ring-shaped, has an open central portion, and is coaxial withand of larger diameter than said motor, whereby the heat of the flame ofsaid blower will tend to pass around said motor in a cylindrical sheath,and whereby said motor will be blanketed at all times with relativelyunheated air drawn through the central opening of said burner.

6. The combination as recited in claim 5 with the addition of anopen-ended tube of smaller diameter than the internal diameter of thering-shaped burner and mounted coaxially with said burner, said tubeextending from a point substantially within said burner to a pointsubstantially forward of said burner and adjacent said motor.

7. The combustion as recited in claim 5 with the addition of anopen-ended tube of smaller diameter than the internal diameter of thering-shaped burner and mounted coaxially with said burner, said tubeextending from a point substantially within said burner to a pointsubstantially forward of said burner and adjacent said motor, and afrustro-conical baffle plate secured around its smaller diameter to therearward end of said tube and diverging forwardly to a diametersubstantially equal to the internal diameter of the burner ring, andterminating forwardly of said burner ring.

8. The combination as recited in claim 1 wherein said housing iscomposite and comprises a tubular blower housing in which said blower ismounted and a tubular burner housing in which said burner is mounted,said blower and burner housings being disposed in end-to-end relationwith the burner housing at the intake end of said blower housing, andmeans for connecting said housings together, said connecting meanscomprising a plurality of radially extending fins secured to said burnerhousing and a fastener secured to each of said fins and engaging saidblower housing, said fasteners being radially adjustable along said finswhereby said burner housing may be selectively mounted on blowerhousings of various diameters.

References Cited in the file of this patent UNITED STATES PATENTS1,629,253 Breese May 17, 1927 2,174,663 Keller Oct. 3, 1939 2,432,525Kruse Dec. 16, 1947 2,460,983 Hess Feb. 8, 1949 2,604,312 Andersen et a1July 22, 1952 2,606,014 Baumann Aug. 5, 1952 2,654,219 Zaba Oct. 6, 19532,703,706 Bishop Mar. 8, 1955 2,836,409 Harrison May 27, 1958 2,966,347Wolfiradt Dec. 27, 1960 FOREIGN PATENTS 323,458 Switzerland July 31,1957

